US3866207A - Apparatus for displaying image informations - Google Patents

Abstract

Disclosed is an apparatus for displaying image informations using a storage tube as a memory device. According to this invention ''''writing'''' of informations in the storage tube is performed in the ''''Semi-random Scanning'''' mode in which raster scanning is performed in one of the vertical and horizontal directions whereas random scanning is conducted in the other direction.

Description

United States Patent 119 1 MODE SELECTION CT.

BEAM CURRENT CONTROL CT.

BEAM ON/OFF CT.

'Goto et al. 1 Feb. 11, 1975 [54] APPARATUS FOR DISPLAYING IMAGE 3,130,397 4/1964 Simmons 340/324 AD N 3,281,822 10/1966 Evans 340/324 AD INFORMATIO u 3,336,498 8/1967 Castanera 340/324 AD 1 Inventors: Eii'chl G010, Futlsawa; H hme 3,380,028 4/1968 Gustafson et al. 340/324 A Ohiwa, Tokyo; Kansei Iwata, 3,514,616 5/1970 Kolb 340/324 AD Tokyo; Tadao Urano, Tokyo, all of Japan Primary Examiner-Donald J. Yusko [73] Assignees: Rlkagaku Kenkyusho, Saitama-ken; Assistant Examiner Marshan M. Curtis hats Elecmc Tokyo Attorney, Agent, or Firm-Bucknam and Archer both of, Japan [22] Filed: Nov. 24, 1972 [21] Appl. No.: 308,947 [57] ABSTRACT [30] Foreign Application Priority Data Disclosed is an apparatus for displaying image infor- J 4 34 mations us ng a storage tube as a memory device. Ac- NOV. 24, apan t 8 cording to invention writing of informations in t the storage tube is performed in the Semi-random g i 340/324 g g g ij Scanning mode in which raster scanning is performed l 315/18 in one of the vertical and horizontal directions I I 0 mm whereas random scanning is conducted in the other 315/11, 12; 178/DIG. 24, 7.7 direction [56] References Cited 6 Cl D F UNlTED STATES PATENTS 'awmg gums 2,595,646 5/l952 Doba, Jr. et al. 340/324 AD STORAGE TUBE HORIZONTAL DEFLECTION CT.

HORIZONTAL COUNTER VERTICAL VIDEO AMPLIFIER DEFLECTION CT.

CRT DISPLAY SYSTEM WITH D-A CONVERTER CT.

HORIZONTAL AND VERTICAL SCAN PAIENIEU FEBI I 5 FIG.

MODE SELECTION CT.

BEAM CURRENT CONTROL CT.

BEAM ON/OFF CT.

STORAGE TUBE HORIZONTAL DEFLECTION CT.

HORIZONTAL COUNTER VERTICAL DEFLECTION CT.

VIDEO AMPLIFIER D A CONVERTER CT.

CRT DISPLAY SYSTEM WITH HORIZONTAL AND VERTICAL SCAN VERTICAL COUNTER FIG. 2

1 APPARATUS FOR DISPLAYING IMAGE INFORMATIONS This invention generally relates to. an apparatus for displaying image informations, and more particularly to a CRT display apparatus for alphanumeric and graphic patterns in an information processing apparatus such as an electronic computer.

Generally speaking, there are two different methods in providing alphanumeric and graphic representations, that is, random scanning and raster scanning. In the random scanning the electron beam of the CRT traces the contours of an alphanumeric or graphic pattern which is being displayed. In the raster scanning the electron beam while being deflected, is intensitymodulated so as to give an alphanumeric or graphic pattern on the phosphor screen of the CRT in the same manner as in the conventional television system.

In the random scanning, display commands are stored in a high-speed memory device such as a core storage, and the display commands so stored are successively interpreted, thus finally producing appropriate deflection signals in the form of electric current or potenial to provide a desired pattern on the phosphor screen of the CRT.

It is necessary to read and display a single command repeatedly at a relatively high repetition rate, or specif ically more than thirty times per second because otherwise, the appearance of flicker would be inevitable. In the random scanning process the preparation ofa chain of commands according to which a desired pattern is to be displayed on the CRT is much easier than in the ras- 'ter scanning process. Because a chain of commands can be prepared'in the same mode of procedure as a person draws pictures on a blackboard. The random scanning process, however, has the defects or disadvan tages as follows:

1. Exclusive use of an expensive high-speed memory device only for reproduction of images 2. Poor capability for displaying complex patterns (Increase of the length of contour line beyond a certain limit will be the cause for flicker.)

3. Requirement for a high speed deflection circuit which permits quick movement of the electron beam to display complex patterns.

As seen for the points as listed above, the random scanning type display system is inevitably expensive.

As for the raster scanning system, informations of intensity modulation of all the scanning lines of the raster of the CRT are stored in a sequential memory such as a disk or a drum, and the informations thus stored are sequentially read out at a rate that causes no flicker effect (for instance, thirty times per second) on the CRT. In this image displaying system, contrary to the random scanning system there is no limit to the length of the contour of an image to be displayed, and therefore no matter what a complicated pattern it may be, it will be displayed with high fidelity. Also, it is advantageous that a commercial television set may be used without incorporating extra elaborated deflection circuit, and therefore the raster scanning system is inexpensive.

The defects or disadvantages of this system, however, are as follows:

1. Time-wasting and difficult work required for preparing bit patterns according to which a desired pattern is to be displayed.

2. Storage capacity of a disk being too large, compared with the video-information of a single CRT. (Ordinarily ten or more CRTs are used in association with a single disk with a view to making full use of the storage capacity of the disk).

3. Simultaneous operation of CRTs of the number which makes full use of the storage capacity of a disk being impossible without using a large-sized computer system 4. Expensive transmission lines, such as coaxial cables being required for conveying video-signals from a computer to the associated CRTs in instances where the CRTs are at a distant place from the computer.

The apparatus for displaying image informations according to this invention makes full use of the merits of both scanning systems.

More specifically, this invention uses in place of a disk, a storage tube in which an electron beam is used for reading or writing of informations. In such a storage apparatus the target plate is put in a proper condition to store a desired pattern upon the impingement of the electron beam against the target, and the pattern thus stored can be read out in the form of electric signal by exposing the target to the electron beam bombardment.

In instances where a storage tube is used as an image storage apparatus, the majority part of the deflection circuit may be used both for the CRT and the storage tube in common with each other, and this is advantageous from the economical point of view. The use and simultaneous operation of a plurality of CRTs. for the reasons mentioned in above item (2) is unecessary.

Since one storage tube can be allotted to one CRT, a storage tube can be positioned in the vicinity of the associated CRT, and therefore even in instances where a computer is positioned at a distant place from the CRT the transmission of write commands from the computer to the storage tube may be performed at a low speed. Thus, no expensive transmission line is required.

Ordinarily, the writing" of information in the storage tube is conducted in the random scanning mode. As a matter of course this requires a deflection circuit capable of interpreting a chain of commands and of generating deflection signals. Advantageously a single (or non-repetative) drawing of the pattern suffices to the storage thereof, as is utterly different from the random scanning CRT. Therefore, there is no problem for flickering, and any desired pattern can be stored no matter what complex pattern it may be. The use of a high speed deflection circuit will permit the substantial reduction of writing time.

In contrast with this, the writing of informations in the storage tube can be conducted in the raster scanning mode if the associated deflection circuit is used both for reading and writing in common.

In operation, the storage tube is put into the writing condition at the time when the deflection circuit deflects the electron beam to a place on which the writing" is to be performed, and then the electron beam is allowed to impinge upon the target plate. Thus, the storage tube functions in the same way as the se quential memory.

As mentioned above, there are two different methods for carrying out writing on the storage tube. In one method similar to sequential storage, writing" is performed at a selected time while the raster scanning is ing is performed in a similar fashion to random access memory.

The inventors employs a totally new method for carrying out writing to the target of the storage tube. In a storage tube it is possible to locate a given point or position in terms of two-dimensional coordinates. Therefore, it is possible that one of the ordinates and abscissas is random-scanned whereas the other is raster-scanned to fix a given point on the target of the storage tube. This new type scanning method is called hereinafter Semi-random Scanning". In an information displaying apparatus according to this invention the informations are written in Semi-random Scanning mode. In the following explanation pertaining to Semi-random Scanning, simply for the benefit of simplicity the raster scanning is used for the horizontal deflection whereas the random scanning is used for the vertical deflection.

In the semi-random scanning system the conventional horizontal deflection circuit can be used for the raster scanning without modification. Assume that the repetition rate of horizontal deflection is fl-I and that the number of abscissa points on a single horizontal line is N An N counter used is driven by clock pulses which are supplied at the repetition rate of N X f,,,'and this counter generates an overflow-pulse every time when the counter has counted N The horizontal deflection circuit is'controlled by overflow pulses, which are used as synchronization pulse, and therefore the content of-the counter is an indication of the coordinate position of the deflected electron beam.

Assume that the number of horizontal lines is N the content of an N -counter is digital-to-analog converted in the form of electric current or potential, which is used to deflect the electron beam in the vertical direction. Thus, the random scanning in the vertical direction can be performed by setting a desired number in the counter.

An N -counter may be a N, bit register. However, raster scanning is required in reading operation, and therefore a counting circuit if used, will perform reading as well as writing.

The relatively slow verticl scanning is performed by digital-to-analog converting the content of the vertical counter. This drastically increases the vertical writing speed, and at the same time facilitates the vertical writing, compared with the writing" by raster scanning. It is adequate that the digital-to-analog converter which is used in writing by Semi-random Scanning provides deflection current or potential within the fly-- back time of the horizontal deflection saw tooth signal (approximately microseconds). Because of the relatively long time within which the deflection current or potential is to be supplied, the digital-to-analog converter is easily designed and constructed.

Still advantageously, the deflection circuit of the commercial television set can be used as the horizontal deflection circuit in the display apparatus of this invention without modification.

Thus, the deflection circuit in the display apparatus of this invention using the Semi-random Scanning is much simpler and less expensive than that in the display apparatus using the two-dimensional random scanning. The performance of the former is by no means inferior to that of the latter, andfor instance in respect 0f the mode of blotting out which will be later described in detail, the former is superior to the latter.

As shown in FIG. 1, the main parts of the display apparatus of this invention using the Semi-random Scanning" are: a vertical counter, a digital-to-analog converter connected to the vertical counter, a vertical deflection circuit connected to the digital-to-analog con- .verter, a vertical deflection circuit connected to the digital-to-analog converter, a horizontal counter, a horizontal deflection circuit connected to the horizontal counter, a storage tube for storing image informations and a display CRT, and the vertical deflection circuit and the horizontal deflection circuit are connected to the storage tube. The CRT is connected to the horizontal counter, the digital-to-analog converter and the storage tube.

In operation, the horizontal delfection circuit supplies a train of saw-tooth signals (horizontal deflection signals) to the storage tube under the control of horizontal synchronizing pulses from the horizontal counter, thus causing the horizontal deflection of the electron beam in the storage tube. The vertical deflection circuit functions to digital-to-analog convert the content of the vertical counter, thus generating vertical deflection signals which will cause the electron beam to deflect in the vertical direction in the storage tube.

A mode selection circuit and a beam on/off circuit and a beam current control circuit are connected to the storage tube. The mode selection circuit is selectively set for one of writing, reading and erasing. The beam current control circuit permits the half-tone writing. The beam on/off circuit allows the electron beam to impinge upon the target at controlled intervals to perform writing or erasing, and the circuit allows the electron beam to continuously impinge upon the target for the sweeping period of the horizontal deflection to perform reading of the stored information.

A video-amplifier is connected between the storage tube and the display CRT. The horizontal synchronizing pulses from the hroizontal counter and the analog signals corresponding to the content of the vertical counter are applied to the deflection circuit of the display CRT, and at the same time the image signals from the storage tube after amplified by the video-amplifier are supplied to the image circuit of the display CRT, thus causing the information stored in the storage tube to appear on the CRT.

In the display system of this invention a light-pen may be used to indicate a given coordinate point on the face plate of the storage tube.

This invention will be better understood from the 'follwong description when considered in connection with the accompanying drawing in which:

FIG. 1 shows a block diagram of the whole system according to this invention; and

FIG. 2 is an explanatory representation as to how a given domain is determined on the display CRT.

Referring to FIG. 1, a mode selection circuit functions to control the voltage which is applied to the targetof the storage tube, thus putting the storage tube in one of three different modes, Reading, Erasing and Writing. In a preferred embodiment using a Lithocon (trade name) produced by Princeton Electric Products Company the storage tube is put in the mode of Reading" by setting the target voltage at the level of six volts above the cathode voltage. Likewise, the

storage tube is put in the mode of Erasing by setting the target voltage at the level of twenty volts-above the cathode voltage, and in the mode of Writing by setting the target voltage at the level of 60 to 300 volts.

In the mode of Reading, proper clock pulses are applied to the horizontal counter, thus causing the same to, generate horizontal synchronizing pulses. In instances where an ordinary television receiver is used for a display apparatus, clock pulsesare so controlled that the repetition rate of horizontal synchronizing pulses is equal to 15.75 KHz. The horizontal synchr'o nizing pulses are applied to the horizontal deflection circuit which is used to deflect the electron beam in the horizontal direction. A horizontal deflection circuit of a videcon camera can be used without modification. Horizontal synchronizing pulses are applied to the vertical counter as clock pulses. The vertical deflection of the electron beam is performed by digital-to-analog converting content of the vertical counter and by applying electric signals thus obtained in the form of voltage or current to the vertical deflection circuit after amplified. Thus, the.two-dimensional scanning can be performed over the target of the storage tube (or the information-storing surface), and if a beam current is set for a proper value by a beam current control circuit (for instance, by applying a voltage of a proper value to the first grid electrode of the storage tube), and if the electron beam of the proper value is allowed to eject by setting the cathode voltage to zero, the stored'informations are successively read" and finally they appear in the output of the video-amplifier. The horizontal synchronizing pulses and the electric signals digital-toanalog converted from the content of the vertical counter are applied to the deflection circuit of the CRT of the television receiver, and at the same time the video-signals from the storage tube are applied to the video-amplifier of the television receiver, thus causing the information stored in the storage tube to appear on the CRT.

What is important in the display CRT is that: a particular storage position of the information bearing surface or target of the storage tube exactly corresponds to a point of the information displaying surface or phosphor screen of the CRT in one-to-one relationship. The content 'of the horizontal counter and that of the vertical counter are shown in terms of the abscissa and ordinate of the co-ordinate system respectively.

In the mode of erasing informations from the storage tube, the mode selection circuit is set for that purpose. and the electron beam is allowed to scan the target surface of the storage tube for a fixed time (sufficient to supply the amount of electron beam which is requirred for erasing). If the electron beam is set at a relatively large value, the erasing time required will accordingly decrease.

In the mode of writing the mode selection circuit is set for writing, and thee beam current contron circuit is adjusted according to the intensity instruction, I

thus finally setting the electron beam of writing at a predetermined value. In instances where an information is stored at either of black and white levels, it suffices that the beam current control circuit is set for a predetermined state. Assume that the domain in which informations are to be stored is as large as the abscissa range H s H s H times the ordinate range V V & V as shown in FIG. 2. In view of the fact that the television scanning is performed in the descending direction, the ordinate is graduated increasingly in the same direction. First, the vertical counter is set at V and clock pulses are applied to the horizontal counter. When the horizontal counter has counted upto H the electron beam is turned on, and when the counter has reached H -l-l, the electron beam is turned of thus performing a writing of information at a predetermined intensity on the abscissa H, s H s H at the ordinate V A horizontal overflow pulse causes the count V of the vertical counter to increase by one, and then a similar operation is repeated. This is repeated until the count V of the vertical counter reaches V thus completing writing of informations in the domain earlier mentioned.

In this mode ofwriting" informations can be stored, for instance on a single horizontal line (y V if the vertical count is set at the fixed number, and likewise, informations can be stored, for instance on a single vertical line (x H if H is equal to H Apparently, an information can be stored, for instance on a single point (H V if H, and V, are equal to H and V respectively.

The writing of informations in the horizontal direction is allowed only at a selected time, as is the case in storing informations in a sequential memory. In contrast to this, the writing of information in the vertical direction is allowed at all times, as is the case in storing informations in a random access memory.

In a preferred embodiment of this invention the information stored on the target of the storage tube can be selectively erased by first, putting the apparatus in the erasing condition and second, allowing the electron beam to repeatedly trace a selected part of the stored information in the same fashion as the electron beam writes the selected part until the same disappears.

As is apparent from the above, irrespective as to in which mode ofwriting, reading and erasing the apparatus operates, the horizontal counter continuously performs counting under the control of clock pulses, generating horizontal synchronizing pulses at the repetition rate of 15.75 KI-Iz. The horizontal deflection circuit of the television receiver may be used for horizontal deflection of the electron beam in the storage tube. As for the vertical deflection of the electron beam in the storage tube the vertical deflection of the electron beam is performed within the fly-back time of the horizontal scanning deflection (about 10 microseconds), and because of this relatively long time allowable the digital-to-analog converter is easily designed, compared with that which would be required in random-scanning both in the vertical and horizontal directions. Because of the random-scanning employed in one of the horizontal and vertical directions image informations can be stored at a high speed and with easiness, compared with the instances where image informations are stored in the sequential memory such as the disk.

As mentioned eariler, the television scanning system in which the length of a line to be drawn is not restricted, is advantageous to blotting operation. The apparatus of this invention using Semi-random Scanning is likewise, advantageous to blotting operation. In the random scanning system it is very difficult for an electron beam to draw a line between given two points in such an analogue way that the electron beam is continuously deflected at a given constant speed to draw a line between given points. (If the deflection speed varies, the intensity of the line drawn by the electron beam will accordingly vary.) ln the prior art, as a routine the line is drawn in the form of equivalent zigzag line, and if blotting is carried out in the random scanning system, it is necessary to blot out adjacent points one after another, and therefore ordinarily much time is spent in blotting operation. In contrast with this, the information displaying apparatus of this invention in which a line can be drawn at a high speed in the horizontal direction, will permit the blotting operation to be performed at a high speed.

Still advangenously, since the vertical deflection is performed by digital-to-analog converting the instantaneous content of the vertical counter, the interlaced scanning can be conducted in a cmpletely controllable way. More specifically, the ordinary television system uses analogue signal for vertical deflection in interlaced scanning, and this is the cause for pairing. In contrast with this, in instances where the deflection signals are produced by digital-to-analog converting instantaneous content of the counter, the deflection current is determined accurately or quantitatively and hence the interlaced scanning is stable, or free from pairing.

Although the embodiment is described as employing the raster-scanning in the horizontal direction and the random-scanning in the vertical direction it should be noted that the Semi-random Scanning can be performed in the reversed way.

What is claimed is:

1. Apparatus for displaying image information comprising a memory device to write-in and read-out image information by addressing in terms of two coordinates; a display device utilizing a scanning beam to display image information, said memory device having an image information signal input and-image information signal output, said display device having an image information signal input; circuit means coupling the output of said memory device with the input of said display device to accomodate transmission to the display de- -vice of signals representing image information read-out from the memory device; addressing means associated with said memory device and operable to effect random access to one coordinate of a given information and sequential access to the other coordinate thereof; and scanning circuit means associated with said display device and operable to effect scanning movement of the display device beam to reproduce an image corresponding to the image information content of said image information signal, said display device scanning circuit means being coupled to said addressing means for synchronized operation therewith.

2. Apparatus according to claim 1 wherein said memory device comprises a storage tube, and said addressing means comprises a scanning circuit which includes a vertical deflection circuit driven by a digital-toanalog converter circuit controlled by a digital counter, and a horizontal deflection circuit driven by a digital counter coupled thereto.

3. Apparatus according to claim 2 wherein the display device scanning circuit means is coupled to said digitalto-analog converter circuit and coupled to the digital counter that drives said horizontal deflection circuit.

4. Apparatus according to claim 3 wherein said horizontal deflection circuit is driven by overflow signals supplied by the digitalcounter coupled thereto.

5. Apparatus according to claim 3 including circuit means associated with said memory device and operable to selectively control the beam current of the associated scanning beam, and to selectively set the memory device in any of a plurality of operating modes.

6. Apparatus according to claim 3 wherein the memory device scanning circuit means is operable to effect random scanning in a vertical direction and raster scanning in a horizontal direction.

Claims (6)

1. Apparatus for displaying image information comprising a memory device to write-in and read-out image information by addressing in terms of two coordinates; a display device utilizing a scanning beam to display image information, said memory device having an image information signal input and image information signal output, said display device having an image information signal input; circuit means coupling the output of said memory device with the input of said display device to accomodate transmission to the display device of signals representing image information read-out from the memory device; addressing means associated with said memory device and operable to effect random access to one coordinate of a given information and sequential access to the other coordinate thereof; and scanning circuit means associated with said display device and operable to effect scanning movement of the display device beam to reproduce an image corresponding to the image information content of said image information signal, said display device scanning circuit means being coupled to said addressing means for synchronized operation therewith.

2. Apparatus according to claim 1 wherein said memory device comprises a storage tube, and said addressing means comprises a scanning circuit which includes a vertical deflection circuit driven by a digital-to-analog converter circuit controlled by a digital counter, and a horizontal deflection circuit driven by a digital counter coupled thereto.

3. Apparatus according to claim 2 wherein the display device scanning circuit means is coupled to said digital- to-analog converter circuit and coupled to the digital counter that drives said horizontal deflection circuit.

4. Apparatus according to claim 3 wherein said horizontal deflection circuit is driven by overflow signals supplied by the digital counter coupled thereto.

5. Apparatus according to claim 3 including circuit means associated with said memory device and operable to selectively control the beam current of the associated scanning beam, and to selectively set the memory device in any of a plurality of operating modes.

6. Apparatus according to claim 3 wherein the memory device scanning circuit means is operable to effect random scanning in a vertical direction and raster scanning in a horizontal direction.

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